Olefin polymerization catalyst having a multidentate ligand

Abstract: Disclosed is an olefin polymerization catalyst comprising a transition metal selected from metals of Groups IIIA including the lanthanide series, IVA, VA, VIA, VIIA and VIII of the Periodic Table of the Elements, and ligands L¹ and L² bonded thereto, wherein a combination of L¹ and L² is (1) a combination of ligand L¹ which is a group containing at least one phosphorus-containing group and ligand L² which is a ligand having a σ-bond, or a ligand having a σ-bond and a bond selected from at least one π-bond and at least one lone electron pair donative bond; (2) a combination of ligand L¹ which is a 5-membered heterocyclic pentadentate ligand having one or more heteroatoms and ligand L² which is a ligand having a σ-bond, or a ligand having a σ-bond and a bond selected from at least one π-bond and at least one lone electron pair donative bond, provided that when the pentadentate ligand contains only one heteroatom, L² is a ligand having a σ-bond, or a ligand having a σ-bond and at least one lone electron pair donative bond; and (3) a combination of ligand L¹ which is a trispyrazolyl tridentate ligand and ligand L² which is an alkapolyenyl ligand, and wherein each L¹ contains an element of Group VB or Group VIB. The catalyst of the present invention has extremely high catalytic activity for an olefin polymerization reaction as compared to conventional olefin polymerization catalysts.

Description: BACKGROUND OF THE INVENTION Field of The Invention The present invention relates to an olefin polymerization catalyst having a multidentate ligand. More particularly, the present invention is concerned with an olefin polymerization catalyst comprising at least one transition metal compound selected from compounds of formulae I and II: wherein M is a transition metal selected from the group consisting of metals of Groups IIIA including the lanthanide series, IVA, VA, VIA, VIIA and VIII of the Periodic Table of the Elements; X is an anionic ligand; n is an integer represented by formula G-2 in which G is the Group number of the Group of the Periodic Table to which the transition metal belongs; J is a non-coordinating anion; and ligand L 1 is a group containing at least one phosphorus-containing group and ligand L 2 which is selected from a ligand having a σ-bond and a ligand having a σ-bond and a bond selected from at least one π-bond and at least one lone electron pair donative bond; wherein L 1 contains an element of Group VB or Group VIB of the Periodic Table of the Elements. The catalyst of the present invention has extremely high catalytic activity for an olefin polymerization reaction as compared to conventional olefin polymerization catalysts. Therefore, by the use of the catalyst of the present invention, a desired olefin polymer can be produced efficiently with a high productivity per unit weight of the catalyst. The olefin polymerization catalyst of the present invention is also advantageous in that it has high heat stability, that the olefin polymer produced has high molecular weight, high bulk density and improved powder characteristics, and that the molecular weight of the olefin polymer can be controlled and the amount of an auxiliary catalyst which is optionally employed can be reduced. Discussion of Related Art In the polymerization of an olefin, it is known to employ as a catalyst a compound having a monodentate ligand comprised of nitrogen as a heteroatom and having a single alkadienyl ligand. For example, Journal "Organometallics" 9 , 867 (1990) discloses the polymerization of an olefin in which use is made of a catalyst comprised of a metal of Group IIIA of the Periodic Table in which the catalyst has a heteroatom monodentate ligand and, bridge-bonded thereto, an alkadienyl ligand. Unexamined Japanese Patent Application Laid-Open Specification No. H3-163088 (corresponding to European Patent Application Publication No. 416815) discloses the polymerization of an olefin in which use is made of a catalyst comprised of a transition metal in which the catalyst has a ligand containing no π-bond and, bridge-bonded thereto, a single ligand having at least one delocalized π-bond, and a formula shown in this Japanese patent document indicates that the ligand containing no π bond is a monodentate ligand. Further, Unexamined Japanese Patent Application Laid-Open Specification No. H3-188092 (corresponding to European Patent Application Publication No. 420436 and U.S. Patent No. 5,055,438) discloses the polymerization of an olefin in which use is made of a catalyst comprised of a metal of Group IVA of the Periodic Table in which the catalyst has a heteroatom ligand and a cyclopentadienyl ligand, and a formula shown in this Japanese patent document indicates that the heteroatom ligand is a monodentate ligand. However, the catalytic activities of these conventional catalysts are extremely low. The catalyst disclosed in the above-mentioned Unexamined Japanese Patent Application Laid-Open Specification No. H3-163088 exhibits a relatively high catalytic activity, but even in the case of this catalyst, the catalytic activity is still unsatisfactory. Illustratively stated, in Working Example 1 of Unexamined Japanese Patent Application Laid-Open Specification No. H3-163088, an olefin polymerization reaction is performed using a catalyst having a monodentate nitrogen ligand and, bridge-bonded thereto, a cyclopentadienyl ligand in order to produce an atactic polypropylene, but the yield of the polymer produced is as small as less than 100 g/g of the metal of the catalyst per hour. Unexamined Japanese Patent Application Laid-Open Specification No. H1-95110 (corresponding to U.S. Patent No. 4,870,042) discloses the polymerization of an olefin, using as a catalyst a reaction product between an alkali metal salt of pyrazolyl borate (containing nitrogen as a heteroatom) and a halide of titanium or zirconium, and aluminoxane as an auxiliary catalyst. In Working Example 3 of the above-mentioned unexamined Japanese patent document No. H1-95110, polyethylene is produced using as a catalyst a reaction product between potassium hydrotrispyrazolyl borate and titanium chloride, but the catalyst is extremely low in catalytic activity, so that the yield of the polyethylene produced under a 1 atm. ethylene pressure is as small as less than 200 g/g of the metal of the catalyst per hour. Unexamined Japanese Patent Application Laid-Open Specification No. H4-305585 (corresponding to European Patent Application publication No. 482934 and U.S. Patent No. 5,237,069) discloses a catalyst comprised of an organometallic compound having a hydrotris(pyrazolyl)borate ligand (containing nitrogen as a heteroatom) and an anionic ligand, and describes that examples of ligands do not include a functional cyclopentadienyl ligand. The catalyst of the above-mentioned unexamined Japanese patent document No. H4-305585 is improved in catalytic activity to some extent, but the yield of polystyrene produced using this catalyst is still as small as less than 4 kg/g of the metal of the catalyst per hour. EP-A-0 574 794 discloses an organometallic compound for use as a catalyst component for the polymerization of olefins, said compound comprising a transition metal of any one of group 3A to group 8 of the Periodic Table and at least one cyclic ligand containing a heteroatom of group 5A or group 5B of the Periodic Table which is capable of forming a π-bond, wherein said transition metal is bonded to the heterocyclic ligand via said heteroatom and a π-bond. WO 91/13074 disloses an olefin polymerization catalyst composition comprising a trivalent transition metal compound wherein two valencies of the transition metal are filled by bidentate chelating compounds, each of the bidentate chelating compounds having a combined hydrocarbyl constituency such that the trivalent transition metal compound is soluble in hydrocarbon solvents. In Journal of Organometallic Chemistry, Vol. 384 (1990), pages 271-278, organometallic compounds are disclosed which have 5-membered heterocyclic ligands each containing one heteroatom. In Journal of Organometallic Chemistry, Vol. 193 (1980), pages C13-16, organometallic compounds are described which have a 5-membered heterocyclic ligand. Another ligand of the respective compounds is a cyclopentadienyl ligand. Further, due to the low catalytic activity of the conventional catalysts which have a monodentate ligand containing nitrogen as a heteroatom or a tridentate ligand containing nitrogen as a heteroatom, such as a trispyrazole borate ligand, the conventional catalysts need to be used in a large amount, so that additional cumbersome operations are needed, such as deashing of an olefin polymer produced (i.e., removal of a catalyst from the olefin polymer produced). Therefore, the conventional olefin polymerization catalysts are unsatisfactory for use in commercially producing olefin polymers. SUMMARY OF THE INVENTION The present inventors have made extensive and intensive studies with a view toward developing a novel olefin polymerization catalyst which is free from the above-mentioned problems inevitably accompanying the conventional olefin polymerization catalysts which have a monodentate ligand containing nitrogen as a heteroatom or a tridentate ligand containing nitrogen as a heteroatom, such as a trispyrazolyl borate ligand. As a result, it has unexpectedly been found that a novel olefin polymerization catalyst comprising a transition metal selected from the group consisting of metals of Groups IIIA including the lanthanide series, IVA, VA, VIA, VIIA and VIII of the Periodic Table of the Elements, and ligands L 1 and L 2 bonded thereto, wherein the ligand L 1 is a tridentate ligand (such as a phospholyl ligand) containing as a heteroatom an element of Group VIB of the Periodic Table, such as phosphorus or oxygen, and the ligand L 2 is a multidentate ligand, such as an alkapolyenyl alkyl group ligand or a monodentate ligand, such as a halogen ligand, exhibits extremely high catalytic activity for olefin polymerization. That is, the above-mentioned novel olefin polymerization catalyst having a specific multidentate ligand exhibits an extremely high catalytic activity for olefin polymerization, as compared to the conventional olefin polymerization catalysts which have a monodentate nitrogen ligand as a heteroatom or a tridentate ligand containing nitrogen as a heteroatom (such as a trispyrazolyl borate ligand) but have no alkapolyenyl ligand (such as a cyclopentadienyl ligand). Further, as compared to the conventional olefin polymerization catalysts, the above-mentioned novel catalyst of the present invention is also advantageous in that it has high heat stability, that an olefin polymer produced has a high molecular weight, high bulk density and improved powder characteristics, that the molecular weight of the olefin polymer can be controlled simply by adding hydrogen and that the amount of alkylaluminoxane as an auxiliary catalyst which may be optionally employed can be reduced. Furthermore, by virtue of the high catalytic activity of the above-mentioned novel catalyst, the amount of a catalyst to be used for an olefin polymerization can be largely reduced, so that there is no need for additional cumbersome operations, such as deashing of a produced olefin polymer (i.e., removal of a catalyst from the polymer). Based on these novel findings, the present invention has been completed. Accordingly, it is a primary object of the present invention to provide a novel olefin polymerization catalyst which is not only extremely high in catalytic activity but also renders it possible to produce an olefin polymer having a desired molecular weight and excellent properties. The foregoing and other objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed description and appended claims. DETAILED DESCRIPTION OF THE INVENTION According to the present invention, there is provided an olefin polymerization catalyst comprising at least one transition metal compound selected from compounds of formulae I and II: wherein: M is a transition metal selected from the group consisting of metals of Groups IIIA including the lanthanide series, IVA, VA, VIA, VIIA and VIII of the periodic Table of the Elements, X is an anionic ligand, n is an integer represented by formula G-2 in which G is the Group number of the Group of the Periodic Table to which the transition metal belongs, and L 1 and L 2 are ligands defined below, wherein a bridge bond is optionally formed between L 1 and L 2 ; and wherein: M, X, n, L 1 and L 2 are as defined for formula (I), and J is a non-coordinating anion. Ligand L 1 is a group, containing at least one phosphorus-containing group, represented by formula III: wherein: A is a carbon atom, or a boron atom substituted with a substituent selected from the group consisting of: a hydrogen atom, a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group or at least one halogen atom, a C 6 - C 20 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group or at least one halogen atom, an oxy group which is substituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a thio group which is substituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a silyl group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group, at least one C 6 - C 20 aromatic hydrocarbon group or at least one halogen atom, a siloxy group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group, at least one C 6 - C 20 aromatic hydrocarbon group or at least one halogen atom, an amino group which is N,N-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group, and a phosphino group which is P,P-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group; {R 1 R 2 (Q=)P} represents a phosphorus-containing group, in which: P is a trivalent or pentavalent phosphorus atom, each of R 1 and R 2 is monovalent and independently represents a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group or at least one halogen atom, or a C 6 - C 20 aromatic hydrocarbon which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group or at least one halogen atom, and Q is divalent and represents a divalent atom of O, S or Se, or a lone electron pair; and each of Z 1 and Z 2 independently represents a phosphorus-containing group of formula {R 1 R 2 (Q=)P} as defined above, or a pyrazolyl group represented by formula IV: wherein: each of R 3 , R 4 and R 5 independently represents: a hydrogen atom, a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group or at least one halogen atom, a C 6 - C 20 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group or at least one halogen atom, an oxy group which is substituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a thio group which is substituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a silyl group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group, at least one C 6 - C 20 aromatic hydrocarbon group or at least one halogen atom, a siloxy group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group, at least one C 6 - C 20 aromatic hydrocarbon group or at least one halogen atom, an amino group which is N,N-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group, and a phosphino group which is P,P-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group, wherein a bridge bond is optionally formed between R 3 and R 4 or between R 3 and R 5 , and ligand L 2 is selected from the group consisting of a ligand having a σ-bond and a ligand having a σ-bond and a bond selected from the group consisting of at least one π-bond and at least one lone electron pair donative bond. The "Periodic Table of the Elements" referred to herein is the Periodic Table of the Elements described in "Kagaku Binran (Chemistry Handbook)", the third revised edition, the fourth print, edited by the Chemical Society of Japan and published by Maruzen Co. Ltd., Japan. Accordingly, the "Groups" and "series" used herein are in accordance with the above-mentioned Periodic Table of the Elements. Examples of anionic ligand X in formulae (I) and (II) include a hydrogen atom; a halogen atom, such as a fluorine atom, a chlorine atom, a bromine atom or an iodine atom; a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group or at least one halogen atom; a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group or at least one halogen atom; an oxy group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group; a thio group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group; a silyl group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 - C 10 aromatic hydrocarbon group, or at least one halogen atom; a siloxy group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 - C 10 aromatic hydrocarbon group, or at least one halogen atom. As illustrative examples of unsubstituted or substituted aliphatic and aromatic hydrocarbon groups employable as ligand X, there can be mentioned a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, a cyclopentyl group, an isopentyl group, a neopentyl group, a hexyl group, a cyclohexyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, a pentadecyl group, a cyclohexenyl group, a cyclohexenylmethyl group, a norbornenyl group, a phenyl group, a tolyl group, an ethylphenyl group, a xylyl group, an isopropylphenyl group, a naphthyl group, a methylnaphthyl group, a biphenyl group, an anthracyl group, a benzyl group, a phenethyl group, a phenylpropyl group, a naphthylmethyl group, a trichloromethyl group, a trifluoromethyl group, a pentafluoroethyl group, a hexafluorocyclohexyl group, a chlorophenyl group, a hexafluorophenyl group, a chloronaphthyl group, a bromonaphthyl group, a p-trichloromethylphenyl group, a p-fluorophenylmethyl group, and a pentachlorobenzyl group. Illustrative examples of substituted oxy groups include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a hexyloxy group, a cyclohexyloxy group, a decyloxy group, a phenoxy group, a naphthoxy group, a tolyloxy group, a methylnaphthoxy group, a benzyloxy group, and a phenethyloxy group. Illustrative examples of substituted thio groups include a methylthio group, an ethylthio group, a propylthio group, a butylthio group, a hexylthio group, a cyclohexylthio group, a decylthio group, a phenylthio group, a naphthylthio group, a tolylthio group, and a methylnaphthylthio group. Illustrative examples of substituted silyl groups include a trimethylsilyl group, a triethylsilyl group, and a phenyldimethylsilyl group. Illustrative examples of substituted siloxy groups include trimethylsiloxy group, a triethylsiloxy group, and a phenyldimethylsiloxy group. Further examples of anionic ligand X in formulae (I) and (II) include an N,N-disubstituted amino group and a P,P-disubstituted phosphino group which are, respectively, represented by formulae (VII) and (VIII): -NR 2 -PR 2 wherein each R is monovalent and independently represents a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or a C 6 - C 20 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group and wherein a bridge bond is optionally formed between the two Rs. Illustrative examples of N,N-disubstituted amino groups include a dimethylamino group, a diethylamino group, an ethylmethylamino group, a diisopropylamino group, a di(t-butyl)amino group, a dicyclohexylamino group, a diphenylamino group, a ditolylamino group, a pyrrolyl group, a pyrazolyl group, and an imidazolyl group. Illustrative examples of P,P-disubstituted phosphino groups include a dimethylphosphino group, a diethylphosphino group, a dipropylphosphino group, a diisopropyl phosphino group, a dicyclohexylphosphino group, a diphenylphosphino group, a bis(p-fluorophenyl)phosphino group, a dibenzylphosphino group, a methylphenylphosphino group and an ethylphenylphosphino group. With respect to the non-coordinating anion represented by [J] - in formula II, any anion can be employed as long as the anion is stable under reaction conditions and is incapable of or hardly capable of forming a coordinate bond with transition metal M in formula II. Examples of such anions include halogenates, such as chlorate, bromate, iodate, perchlorate, perbromate and periodate; tetra-substituted borotes, such as tetrafluoroborate, tetraphenylborate, tetrakis(p-fluorophenyl)borate, tetrakis(p-chlorophenyl)borate, tetrakis(pentafluorenyl)borate, tetratolylborate and tetrakis(2,4-dimethylphenyl)borate; polyborates, such as octadecaborate, tridecahydride-7-carbaundecaborate, bis(7,8-dicarbaundecaborate)cobaltate, bis(undecahydride-7,8-dicarbaundecaborate)nickelate and 1-carbadodecaborate; halide anions of Group VB of the Periodic Table, such as hexafluorophosphate and hexafluoroantim onate; tellurates, such as pentafluoroxotellurate; heteropoly anions, such as phosphotungstate and silicotungsate; a fullerene anion; and a methylenebistrifluorosulfonate. Of these, a tetra-substituted borate is especially preferred. Ligand L 1 is a tridentate ligand, containing at least one phosphorus-containing group, represented by the following formula III: In formula III, A is a carbon atom, or a boron atom substituted with a substituent selected from the group consisting of: a hydrogen atom; a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group or at least one halogen atom; a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group or at least one halogen atom; an oxy group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group; a thio group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group; a silyl group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 - C 10 aromatic hydrocarbon group, or at least one halogen atom; a siloxy group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 - C 10 aromatic hydrocarbon group, or at least one halogen atom; an amino group which is N,N-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group; and a phosphino group which is P,P-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group. In formula III, {R 1 R 2 (Q=)P} represents a phosphorus-containing group, in which: P is a trivalent or pentavalent phosphorus atom; each of R 1 and R 2 is monovalent and independently represents a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or a C 6 - C 20 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group; and Q is divalent and represents a divalent atom of O, S or Se, or a lone electron pair. In formula III, each of Z 1 and Z 2 independently represents a phosphorus-containing group of formula {R 1 R 2 (Q=)P} as defined above, or a pyrazolyl group represented by formula IV: wherein: each of R 3 , R 4 and R 5 independently represents: a hydrogen atom; a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group or at least one halogen atom; a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group or at least one halogen atom; an oxy group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group; a thio group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group; a silyl group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 - C 10 aromatic hydrocarbon group, or at least one halogen atom; a siloxy group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 - C 10 aromatic hydrocarbon group, or at least one halogen atom; an amino group which is N,N-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group; and a phosphino group which is P,P-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group. In formula IV, a bridge bond is optionally formed between R 3 and R 4 or between R 3 and R 5 . Depending upon the types of Z 1 and Z 2 in formula III, tridentate ligands of formula III include the following three types of ligands, namely, a tridentate ligand having three phosphorus-containing groups, a tridentate ligand having two phosphorus-containing groups and one pyrazolyl group and a tridentate ligand having one phosphorus-containing group and two pyrazolyl groups. Of these, a tridentate ligand having three phosphorus-containing groups is especially preferred. Examples of tridentate ligands having three phosphorus-containing groups include trisphosphino compounds, such as tris(dicyclohexylphosphino)methanide and tris(diphenylphosphino)methanide; trisoxophosphorus compounds, such as tris(dicyclohexyloxophosphoranyl)methanide and tris(diphenyloxophosphoranyl)methanide; tristhiophosphorus compounds, such as tris(dicyclohexylthiophosphoranyl)methanide and tris(diphenylthiophosphoranyl)methanide; trisselenophosphorus compounds, such as tris(dicyclohexylselenophosphoranyl)methanide and tris(diphenylselenophosphoranyl)methanide; compounds having two different phosphorus-containing groups, such as bis(diphenylphosphino)(diphenyloxophosphoranyl)methanide, bis(diphenyloxophosphoranyl)(diphenylphosphino)methanide, bis(diphenylphosphino)(diphenylthiophosphoranyl)methanide, bis(diphenylthiophosphoranyl)(diphenylphosphino)methanide, bis(diphenylphosphino)(diphenylselenophosphoranyl)methanide, bis(diphenylselenophosphoranyl)(diphenylphosphino)methanide, bis(diphenyloxophosphoranyl)(diphenylthiophosphoranyl)methanide, bis(diphenylthiophosphoranyl)(diphenyloxophosphoranyl)methanide, bis(diphenyloxophosphoranyl)(diphenylselenophosphoranyl)methanide, bis(diphenylselenophosphoranyl)(diphenyloxophosphoranyl)methanide, bis(diphenylthiophosphoranyl)(diphenylselenophosphoranyl)methanide, and bis(diphenylselenophosphoranyl)(diphenylthiophosphoranyl)methanide; compounds having three different phosphorus-containing groups, such as (diphenylphosphino)(diphenyloxophosphoranyl) (diphenylthiophosphoranyl)methanide, (diphenylphosphino)(diphenyloxophosphoranyl)(diphenylselenophosphoranyl)methanide, (diphenylphosphino)(diphenylthiophosphoranyl)(diphenylselenophosphoranyl)methanide, and (diphenyloxophosphoranyl)(diphenylthiophosphoranyl)(diphenylselenophosphoranyl)methanide. In addition, there can be mentioned compounds having the same nomenclatures as those of the above compounds except that the term "methanide" is replaced with "hydroborate", or "C 1 - C 10 alkyl group-substituted borate". One example of ligand L 2 is a monodentate ligand having a σ-bond, which is selected from the group consisting of: a hydrogen atom; a halogen atom, such as a fluorine atom, a chlorine atom, a bromine atom or an iodine atom; a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group or at least one halogen atom; a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group or at least one halogen atom; an oxy group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group; a thio group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group; a silyl group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 - C 10 aromatic hydrocarbon group, or at least one halogen atom; a siloxy group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 - C 10 aromatic hydrocarbon group, or at least one halogen atom; an amino group which is N,N-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group; and a phosphino group which is P,P-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group. As illustrative examples of unsubstituted or substituted aliphatic and aromatic hydrocarbon groups employable as ligand L 2 , there can be mentioned a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, a cyclopentyl group, an isopentyl group, a neopentyl group, a hexyl group, a cyclohexyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, a pentadecyl group, a cyclohexenyl group, a cyclohexenyl methyl group, a norbornenyl group, a phenyl group, a tolyl group, an ethylphenyl group, a xylyl group, an isopropylphenyl group, a naphthyl group, a methylnaphthyl group, a biphenyl group, an anthracyl group, a benzyl group, a phenethyl group, a phenylpropyl group, a naphthylmethyl group, a trichloromethyl group, a trifluoromethyl group, a pentafluoromethyl group, a hexafluorocyclohexyl group, a chlorophenyl group, a hexafluorophenyl group, a chloronaphthyl group, a bromonaphthyl group, a p-trichloromethylphenyl group, a p-fluorophenylmethyl group, and a pentachlorobenzyl group. Illustrative examples of substituted oxy groups include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a hexyloxy group, a cyclohexyloxy group, a decyloxy group, a phenoxy group, a naphthoxy group, a tolyloxy group, a methylnaphthoxy group, a benzyloxy group, and a phenethyloxy group. Illustrative examples of substituted thio groups include a methylthio group, an ethylthio group, a propylthio group, a butylthio group, a hexylthio group, a cyclohexylthio group, a decylthio group, a phenylthio group, a naphthylthio group, a tolylthio group, and a methylnaphthylthio group. Illustrative examples of substituted silyl groups include a trimethylsilyl group, a triethylsilyl group, and a phenyldimethylsilyl group. Illustrative examples of substituted siloxy groups include trimethylsiloxy group, a triethylsiloxy group, and a phenyldimethylsiloxy group. Further examples of ligand L 2 include an N,N-disubstituted amino group and a P,P-disubstituted phosphino group which are, respectively, represented by formulae VII and VIII: -NR 2 -PR 2 wherein: each R independently represents: a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group; or a C 6 - C 20 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group. In formulae VII and VIII, a bridge bond is optionally formed between two Rs. Examples of the ligands represented by the above formulae VII or VIII include amino groups, such as a dimethylamino group, a diethylamino group, an ethylmethylamino group, a diisopropylamino group, a di(t-butyl)amino group, a dicyclohexylamino group, a diphenylamino group, a ditolylamino group, a pyrrolyl group, a pyrazolyl group and an indazolyl group; phosphino groups, such as a dimethylphosphino group, a diethylphosphino group, a dipropylphosphino group, a diisopropylphosphino group, a dicyclohexylphosphino group, a diphenylphosphino group, a bis(p-fluorophenyl)phosphino group, a dibenzylphosphino group, a methylphenylphosphino group, and an ethylphenylphosphino group. Further examples of ligand L 2 include an N,N-disubstituted amino group and a P,P-disubstituted phosphino group which are, respectively, represented by formulae (IX) and (X): -NR- -PR- wherein R is as defined above for formulae VII and VIII and N or P is bridge-bonded to L 1 . L 2 to be employed in combination with L 1 may be a multidentate ligand having a σ-bond and a bond selected from the group consisting of at least one π-bond and at least one lone electron pair donative bond. As examples of such multidentate ligand L 2 , there can be mentioned alkamonoenyl ligands, such as an alkenyl ligand and a cycloalkenyl ligand; and alkapolyenyl ligands, such as an alkadienyl ligand, a cycloalkadienyl ligand, a cycloalkatrienyl ligand and an alkatrienyl ligand. Further examples of ligand L 2 include a tridentate ligand, containing at least one phosphorus-containing group, represented by the same formula as formula III, a 5-membered heterocyclic pentadentate ligand represented by formula V described below and a trispyrazolyl tridentate ligand represented by formula VI described below. An especially preferred example of multidentate ligand L 2 is a ligand having a monocyclic or polycyclic alkadienyl skeleton represented by the following formula XI: C 5 H 5 - X R X wherein: H represents a hydrogen atom; X represents an integer of from 0 to 5; and each R independently represents: a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group or at least one halogen atom, a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group or at least one halogen atom, an oxy group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a thio group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a silyl group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 - C 10 aromatic hydrocarbon group, or at least one halogen atom, a siloxy group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 - C 10 aromatic hydrocarbon group, or at least one halogen atom, an amino group which is N,N-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group, or a phosphino group which is P,P-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group. Examples of ligands represented by formula XI include a cyclopentadienyl group, a methylcyclopentadienyl group, an ethylcyclopentadienyl group, an n-propylcyclopentadienyl group, an isopropylcyclopentadienyl group, an n-butylcyclopentadienyl group, a trimethylsilylcyclopentadienyl group, a trimethylgermylcyclopentadienyl group, a 1,2-dimethylcyclopentadienyl group and 1,3- or 1,4-substitution isomers thereof, a 1,2,3-trimethylcyclopentadienyl group and substitution isomers thereof, a 1,2,3,4-tetramethylcyclopentadienyl group and substitution isomers thereof, a tetramethylcyclopentadienyl group, an unsubstituted or substituted indenyl group, an unsubstituted or substituted terahydroindenyl group, an unsubstituted or substituted fluorenyl group, and an unsubstituted or substituted octahydrofluorenyl group. The above-mentioned ligands may be bridge-bonded to ligand L 1 . A 5-membered heterocyclic pentadentate ligand to be employed as L 2 is a ligand represented by the following formula V: {E m (CR 6 )5-m} - wherein: each R 6 independently represents: a hydrogen atom, a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group or at least one halogen atom, a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group or at least one halogen atom, an oxy group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a thio group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a silyl group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 - C 10 aromatic hydrocarbon group, or at least one halogen atom, a siloxy group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 - C 10 aromatic hydrocarbon group, or at least one halogen atom, an amino group which is N,N-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group, or a phosphino group which is P,P-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group; m is an integer of from 1 to 5; and each E independently represents a trivalent atom selected from nitrogen, phosphorus, arsenic, antimony and bismuth atoms. In formula V, a bridge bond is optionally formed between neighboring R 6 and R 6 . When E in formula V is a nitrogen atom, examples of L 2 represented by formula V include a pyrrolyl group, and substituted pyrrolyl groups, such as a 2-methylpyrrolyl group, a 3-methylpyrrolyl group, a 2,3-dimethylpyrrolyl group, a 3,4-dimethylpyrrolyl group, a 2,5-dimethylpyrrolyl group, a 2,3,4-trimethylpyrrolyl group, a 2,3,5-trimethylpyrrolyl group, a 2,3,4,5-tetramethylpyrrolyl group, and substituted pyrrolyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a pyrazolyl group, and substituted pyrazolyl groups, such as a 3-methylpyrazolyl group, a 4-methylpyrazolyl group, a 5-methylpyrazolyl group, a 3,4-dimethylpyrazolyl group, a 3,5-dimethylpyrazolyl group, a 3,4,5-trimethylpyrazolyl group, and substituted pyrazolyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; an imidazolyl group, and substituted imidazolyl groups, such as a 2-methylimidazolyl group, a 4-methylimidazolyl group, a 5-methylimidazolyl group, a 2,4-dimethylimidazolyl group, a 2,5-dimethylimidazolyl group, a 2,4,5-trimethylimidazolyl group, and substituted imidazolyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a 1,2,3-triazolyl group, and substituted 1,2,3-triazolyl groups, such as a 4-methyl-1,2,3-triazolyl group, a 5-methyl-1,2,3-triazolyl group, a 4,5-dimethyl-1,2,3-triazolyl group, and substituted triazolyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a 1,3,5-triazolyl group and substituted 1,3,5-triazolyl groups, such as a 2-methyl-1,3,5-triazolyl group, a 3,4-dimethyl-1,3,5-triazolyl group, and substituted 1,3,5-triazolyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a tetrazolyl group, and substituted tetrazolyl groups, such as a 5-methyltetrazolyl group, and substituted tetrazolyl groups having the same nomenclatures as those of the above groups except that the term "methyl " is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; and polycyclic polyazolyl groups, such as an indolyl group, a 4,5,6,7-tetrahydroindolyl group, an indazolyl group, a benzimidazolyl group, a 7-azaindolyl group, a benzotriazolyl group, a 4-azabenzimidazolyl group, a purinyl group, a carbazolyl group, a 1,2,3,4-tetrahydrocarbazolyl group, and cyclic polyazolyl groups which are substituted with a methyl group, an ethyl group, an isopropyl group, a t-butyl group, a cyclohexyl group, a phenyl group, or a trimethylsilyl group. When E in formula V is a phosphorus atom, examples of L 2 represented by formula V include a phospholyl group, and substituted phospholyl groups, such as a 2-methylphospholyl group, a 3-methylphospholyl group, a 2,3-dimethylphospholyl group, a 3,4-dimethylphospholyl group, a 2,5-dimethylphospholyl group, a 2,3,4-trimethylphospholyl group, a 2,3,5-trimethylphospholyl group, a 2,3,4,5-tetramethylphospholyl group, and substituted phospholyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a 1,2-diphospholyl group, and substituted 1,2-diphospholyl groups, such as a 3-methyl 1,2-diphospholyl group, a 4-methyl 1,2-diphospholyl group, a 5-methyl 1,2-diphospholyl group, a 3,4-dimethyl 1,2-diphospholyl group, a 3,5-dimethyl 1,2-diphospholyl group, a 3,4,5-trimethyl 1,2-diphospholyl group, and substituted 1,2-diphospholyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a 1,3-diphospholyl group, and substituted 1,3-diphospholyl groups, such as a 2-methyl 1,3-diphospholyl group, a 4-methyl 1,3-diphospholyl group, a 5-methyl 1,3-diphospholyl group, a 2,4-dimethyl 1,3-diphospholyl group, a 2,5-dimethyl 1,3-diphospholyl group, a 2,4,5-trimethyl 1,3-diphospholyl group, and substituted 1,3-diphospholyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a 1,2,3-triphospholyl group, and substituted 1,2,3-triphospholyl groups, such as a 4-methyl 1,2,3-triphospholyl group, a 5-methyl 1,2,3-triphospholyl group, a 4,5-dimethyl 1,2,3-triphospholyl group, and substituted 1,2,3-triphospholyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a 1,3,5-triphospholyl group, and substituted 1,3,5-triphospholyl groups, such as a 2-methyl 1,3,5-triphospholyl group, a 3,4-dimethyl 1,3,5-triphospholyl group, and substituted pyrrolyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a tetraphospholyl group, and substituted tetraphospholyl groups, such as a 5-methyltetraphospholyl group, and substituted tetraphospholyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a pentaphospholyl group; and polycyclic polyphospholyl groups, such as a benzo[b]-phospholyl group, a 4,5,6,7-tetrahydrobenzo[b]-phospholyl group, a benzo[b]-1,2-diphospholyl group, a benzo[b]-1,3-diphospholyl group, a dibenzo[b,d]phospholyl group, and polycyclic polyphospholyl groups which are substituted with a methyl group, an ethyl group, an isopropyl group, a t-butyl group, a cyclohexyl group, a phenyl group, or a trimethylsilyl group. When E in formula V is an arsenic atom, examples of L 2 represented by formula V include an arsolyl group, and substituted arsolyl groups, such as a 2-methylarsolyl group, a 3-methylarsolyl group, a 2,3-dimethylarsolyl group, a 3,4-dimethylarsolyl group, a 2,5-dimethylarsolyl group, a 2,3,4-trimethylarsolyl group, a 2,3,5-trimethylarsolyl group, a 2,3,4,5-tetramethylarsolyl group, and substituted arsolyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a 1,2-diarsolyl group, and substituted 1,2-diarsolyl groups, such as a 3-methyl 1,2-diarsolyl group, a 4-methyl 1,2-diarsolyl group, a 5-methyl 1,2-diarsolyl group, a 3,4-dimethyl 1,2-diarsolyl group, a 3,5-dimethyl 1,2-diarsolyl group, a 3,4,5-trimethyl 1,2-diarsolyl group, and substituted 1,2-diarsolyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a 1,3-diarsolyl group, and substituted 1,3-diarsolyl groups, such as a 2-methyl 1,3-diarsolyl group, a 4-methyl 1,3-diarsolyl group, a 5-methyl 1,3-diarsolyl group, a 2,4-dimethyl 1,3-diarsolyl group, a 2,5-dimethyl 1,3-diarsolyl group, a 2,4,5-trimethyl 1,3-diarsolyl group, and substituted 1,3-diarsolyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a 1,2,3-triarsolyl group, and substituted 1,2,3-triarsolyl groups, such as a 4-methyl 1,2,3-triarsolyl group, a 5-methyl 1,2,3-triarsolyl group, a 4,5-dimethyl 1,2,3-triarsolyl group, and substituted 1,2,3-triarsolyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a 1,3,5-triarsolyl group, and substituted 1,3,5-triarsolyl groups, such as a 2-methyl 1,3,5-triarsolyl group, a 2,4-dimethyl 1,3,5-triarsolyl group, and substituted 1,3,5-triarsolyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a tetraarsolyl group, and substituted tetraarsolyl groups, such as a 5-methyltetraarsolyl group, and substituted tetraarsolyl groups having the same nomenclature as that of the above group except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; and polycyclic polyarsolyl groups, such as benzo[b]arsolyl group, a 4,5,6,7-tetrahydrobenzo[b]arsolyl group, a benzo[b]-1,2-diarsolyl group, a benzo[b]-1,3-diarsolyl group, a dibenzo[b,d]arsolyl group, and polycyclic polyarsolyl groups which are substituted with a methyl group, an ethyl group, an isopropyl group, a t-butyl group, a cyclohexyl group, a phenyl group, or a dimethylsilyl group. When E in formula V is an antimony atom, examples of ligand L 2 represented by formula V include a stibolyl group, and substituted stibolyl groups, such as a 2-methylstibolyl group, a 3-methylstibolyl group, a 2,3-dimethylstibolyl group, a 3,4-dimethylstibolyl group, a 2,5-dimethylstibolyl group, a 2,3,4-trimethylstibolyl group, a 2,3,5-trimethylstibolyl group, a 2,3,4,5-tetramethylstibolyl group, and substituted stibolyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a 1,2-distibolyl group, and substituted 1,2-distibolyl groups, such as a 3-methyl 1,2-distibolyl group, a 4-methyl 1,2-distibolyl group, a 5-methyl 1,2-distibolyl group, a 3,4-dimethyl 1,2-distibolyl group, a 3,5-dimethyl 1,2-distibolyl group, a 3,4,5-trimethyl 1,2-distibolyl group, and substituted 1,2-distibolyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a 1,3-distibolyl group, and substituted 1,3-distibolyl groups, such as a 2-methyl 1,3-distibolyl group, a 4-methyl 1,3-distibolyl group, a 5-methyl 1,3-distibolyl group, a 2,4-dimethyl 1,3-distibolyl group, a 2,5-dimethyl 1,3-distibolyl group, a 2,4,5-trimethyl 1,3-distibolyl group, and substituted 1,3-distibolyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a 1,2,3-tristibolyl group, and substituted 1,2,3-tristibolyl groups, such as a 4-methyl 1,2,3-tristibolyl group, a 5-methyl 1,2,3-tristibolyl group, a 4,5-dimethyl 1,2,3-tristibolyl group, and substituted 1,2,3-tristibolyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl" , "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a 1,3,5-tristibolyl groups, and substituted 1,3,5-tristibolyl groups, such as a 2-methyl 1,3,5-tristibolyl group, a 2,4-dimethyl 1,3,5-tristibolyl group, and substituted 1,3,5-tristibolyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a tetrastibolyl group, and substituted tetrastibolyl groups, such as a 5-methyltetrastibolyl group, and substituted tetrastibolyl groups having the same nomenclature as that of the above group except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; polycyclic polystibolyl groups, such as a benzo[b]stibolyl group, a 4,5,6,7-tetrahydrobenzo[b]stibolyl group, a benzo[b]1,2-distibolyl group, a benzo[b]-1,3-distibolyl group, a dibenzo[b,d]stibolyl group, and polycyclic polystibolyl groups which are substituted with a methyl group, an ethyl group, an isopropyl group, a t-butyl group, a cyclohexyl group, a phenyl group or a trimethylsilyl group. When E in formula V is a bismuth atom, examples of ligand L 2 represented by formula V include a bismolyl group, and substituted bismolyl groups, such as a 2-methylbismolyl group, a 3-methylbismolyl group, a 2,3-dimethylbismolyl group, a 3,4-dimethylbismolyl group, a 2,5-dimethylbismolyl group, a 2,3,4-trimethylbismolyl group, a 2,3,5-trimethylbismolyl group, a 2,3,4,5-tetramethylbismolyl group, and substituted bismolyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a 1,2-dibismolyl group, and substituted 1,2-dibismolyl groups, such as a 3-methyl 1,2-dibismolyl group, a 4-methyl 1,2-dibismolyl group, a 5-methyl 1,2-dibismolyl group, a 3,4-dimethyl 1,2-dibismolyl group, a 3,5-dimethyl 1,2-dibismolyl group, a 3,4,5-trimethyl 1,2-dibismolyl group, and substituted 1,2-dibismolyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a 1,3-dibismolyl groups, and substituted 1,3-dibismolyl groups, such as a 2-methyl 1,3-dibismolyl group, a 4-methyl 1,3-dibismolyl group, a 5-methyl 1,3-dibismolyl group, a 2,4-dimethyl 1,3-dibismolyl group, a 2,5-dimethyl 1,3-dibismolyl group, a 2,4,5-trimethyl 1,3-dibismolyl group, and substituted 1,3-dibismolyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a 1,2,3-tribismolyl group, and substituted 1,2,3-tribismolyl groups, such as a 4-methyl 1,2,3-tribismolyl group, a 5-methyl 1,2,3-tribismolyl group, a 4,5-dimethyl 1,2,3-tribismolyl group, and substituted 1,2,3-tribismolyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a 1,3,5-tribismolyl group, and substituted 1,3,5-tribismolyl groups, such as a 2-methyl 1,3,5-tribismolyl group, a 2,4-dimethyl 1,3,5-tribismolyl group, and substituted 1,3,5-tribismolyl groups having the same nomenclatures as those of the above groups except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; a tetrabismolyl group, and substituted tetrabismolyl groups, such as a 5-methyltetrabismolyl group, and substituted tetrabismolyl groups having the same nomenclatures as that of the above group except that the term "methyl" is replaced with a term "ethyl", "isopropyl", "t-butyl", "cyclohexyl", "phenyl", or "trimethylsilyl"; polycyclic polybismolyl groups, such as a benzo[b]bismolyl group, a 4,5,6,7-tetrahydrobenzo[b]bismolyl group, a benzo[b]-1,2-dibismolyl group, a benzo[b]-1,3-dibismolyl group and a dibenzo[b,d]bismolyl group, and polycyclic polybismolyl groups which are substituted with a methyl group, an ethyl group, an isopropyl group, a t-butyl, a cyclohexyl group, a phenyl group, or a trimethylsilyl group. Further, when E in formula V is a combination of atoms selected from nitrogen, phosphorus, arsenic, antimony and bismuth atoms , examples of ligand L 2 represented by formula V include a phosphazolyl group, a phosphadiazolyl group, a diphosphadiazolyl group, a phosphatriazolyl group, a diphosphazolyl group, a triphosphazolyl group, an arsazolyl group, a stibazolyl group, a bismazolyl group, an arsaphospholyl group, a stibaphospholyl group, a bismaphospholyl group, a stibaarsolyl group, a bismaarsolyl group, a bismastibolyl group, and groups which can be obtained by substitution of the above groups with an alkyl group, and polycyclic compounds containing the above groups. A trispyrazolyl tridentate ligand to be employed as L 2 is a ligand represented by formula VI: In formula VI, A is defined above for formula III. That is, in formula VI, A is a carbon atom, or a boron atom substituted with a substituent selected from the group consisting of: a hydrogen atom; a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group or at least one halogen atom; a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group or at least one halogen atom; an oxy group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group; a thio group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group; a silyl group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 - C 10 aromatic hydrocarbon group, or at least one halogen atom; a siloxy group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 - C 10 aromatic hydrocarbon group, or at least one halogen atom; an amino group which is N,N-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group; and a phosphino group which is P,P-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group. In formula VI, each of Z 3 , Z 4 and Z 5 independently represents a pyrazolyl group represented by formula IV: wherein: each of R 3 , R 4 and R 5 independently represents: a hydrogen atom; a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group or at least one halogen atom; a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group or at least one halogen atom; an oxy group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group; a thio group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group; a silyl group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 - C 10 aromatic hydrocarbon group, or at least one halogen atom; a siloxy group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 - C 10 aromatic hydrocarbon group, or at least one halogen atom; an amino group which is N,N-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group; and a phosphino group which is P,P-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group. In formula IV, a bridge bond is optionally formed between R 3 and R 4 or between R 3 and R 5 . Examples of such trispyrazolyl tridentate ligands include a hydrotrispyrazolylborate group; and derivatives thereof obtained by substituting the hydro group of the hydrotrispyrazolylborate group with alkyl, aryl or a heterocyclic ring, such as isopropyltrispyrazolylborate, n-butyltrispyrazolylborate, and tetrakispyrazolylborate (Class 1 ligands); Class 1 ligands having monosubstituted pyrazolyl, such as hydrotris(3-isopropylpyrazolyl)borate, hydrotris(3-t-butylpyrazolyl)borate, hydrotris(3-phenylpyrazolyl)borate, and hydrotris(3-(2'-thienyl)pyrazolyl)borate (Class 2 ligands); substitution isomers of Class 2 ligands, such as hydrobis(3-isopropylpyrazolyl)(5-isopropylpyrazolyl)borate and the like (Class 3 ligands); Class 1 ligands having disubstituted pyrazolyl, such as hydrotris(3,5-dimethylpyrazolyl)borate, isopropyltris(3,5-dimethylpyrazolyl)borate, n-butyltris(3,5-dimethylpyarzolyl)borate, tetrakis(3,5-dimethylpyarzolyl)borate, hydrotris(3,5-diisopropylpyrazolyl)borate, isopropyltris(3,5-diisopropylpyrazolyl)borate, n-butyltris(3,5-diisopropylpyrazolyl)borate, tetrakis(3,5-diisopropylpyrazolyl)borate, hydrotris(3,5-diphenylpyrazolyl)borate, isopropyltris(3,5-diphenylpyrazolyl)borate, n-butyltris(3,5-diphenylpyrazolyl)borate, tetrakis(3,5-diphenylpyrazolyl)borate and hydrotris(3-isopropyl-4-bromopyrazolyl)borate (Class 4 ligands); and substitution isomers of Class 4 ligands, such as hydrobis(3-isopropyl-4-bromopyrazolyl)(5-isopropyl-4-bromopyrazolyl)borate; ring-substituted Class 1 ligands, such as hydrotris(7-isopropyl-4-methyl-4,5,6,7-tetrahydro-2-indazoyl)borate (Class 5 ligands). In the present invention, when a bridge bond is formed between L 1 and L 2 , L 1 and L 2 may be bridge-bonded through a divalent group. Examples of such divalent groups through which L 1 and L 2 may be bridge bonded include an alkylene group, such as a methylene group, a diphenylmethylene group, an ethylene group, a propylene group and a cyclohexylene group; a silylene group, and derivatives thereof, such as a dimethylsilylene group and a diphenylsilylene group; a germylene group, and derivatives thereof, such as a dimethylgermylene group and a diphenylgermylene group; and a stannylene group, and derivatives thereof, such as a dimethylstannylene group and a diphenylstannylene group. In the present invention, a bridge bond may be formed within either of ligand L 1 and L 2 through a divalent hydrocarbon group, such as a methylene group, a diphenylmethylene group, an ethylene group, a propylene group, a butenylene group and a cyclohexylene group. The transition metal used in the catalyst of the present invention is selected from the group consisting of metals of Groups IIIA including the lanthanide series, IVA, VA, VIA, VIIA and VIII, more preferably metals of Groups IIIA, IVA, VA of the Periodic Table of the Elements. It is still more preferred that the transition metal used in the catalyst of the present invention is selected from metals of Groups IVA, such as titanium, zirconium and hafnium. The transition metal compound of the catalyst of the present invention is selected from compounds represented by the following formulae XII, XIII, XIV and XV: wherein: M is a transition metal of Groups IVA of the Periodic Table of the Elements, X is an anionic ligand, J is a non-coordinating anion, L 1 and L 2 are ligands described above, and wherein a bridge bond may be formed between ligand L 1 and ligand L 2 . Examples of compounds of formula XII wherein M represents zirconium include those which can be classified into Classes 1 and 2. Class 1 (compounds having a combination of ligand L 1 and ligand L 2 , wherein ligand L 1 is a group containing at least one phosphorous-containing group, represented by formula III and ligand L 2 is selected from the group consisting of a ligand having a σ-bond and a ligand having a σ-bond and a bond selected from the group consisting of at least one π-bond and at least one lone electron pair donative bond): tris(diphenylphosphino)methanidozirconium trichloride, tris(diphenylphosphino)methanidozirconium tribenzyl, tris(diphenylphosphino)methanidozirconium trimethyl, tris(diphenylphosphino)methanidodiisopropylaminozirconium dichloride, tris(diphenylphosphino)methanidodiisopropylaminozirconium dimethyl, tris(diphenylphosphino)methanidodi(t-butyl)aminozirconium dichloride, tris(diphenylphosphino)methanidodi(t-butyl)aminozirconium dimethyl, tris(diphenylphosphino)methanidodicyclohexylaminozirconium dichloride, tris(diphenylphosphino)methanidodicyclohexylaminozirconium dimethyl, tris(diphenylphosphino)methanidodiphenylphosphinozirconium dichloride, tris(diphenylphosphino)methanidodiphenylphosphinozirconium dimethyl, tris(diphenylphosphino)methanidodicyclohexylphosphinozirconium dichloride, tris(diphenylphosphino)methanidodicyclohexylphosphinozirconium dimethyl, tris(diphenylphosphino)methanidocyclopentadienylzirconium dichloride, tris(diphenylphosphino)methanidocyclopentadienylzirconium dimethyl, tris(diphenylphosphino)methanidobutylcyclopentadienylzirconium dichloride, tris(diphenylphosphino)methanidobutylcyclopentadienylzirconium dimethyl, tris(diphenylphosphino)methanidoindenylzirconium dichloride, tris(diphenylphosphino)methanidoindenylzirconium dimethyl, tris(diphenylphosphino)methanidotetrahydroindenylzirconium dichloride, tris(diphenylphosphino)methanidotetrahydroindenylzirconium dimethyl, tris(diphenylphosphino)methanidofluorenylzirconium dichloride, tris(diphenylphosphino)methanidofluorenylzirconium dimethyl, tris(diphenyloxophosphoranyl)methanidozirconium trichloride, tris(diphenyloxophosphoranyl)methanidozirconium tribenzyl, tris(diphenyloxophosphoranyl)methanidozirconium trimethyl, tris(diphenyloxophosphoranyl)methanidodiisopropylaminozirconium dichloride, tris(diphenyloxophosphoranyl)methanidodiisopropylaminozirconium dimethyl, tris(diphenyloxophosphoranyl)methanidodi(t-butyl)aminozirconium dichloride, tris(diphenyloxophosphoranyl)methanidodi(t-butyl)aminozirconium dimethyl, tris(diphenyloxophosphoranyl)methanidodicyclohexylaminozirconium dichloride, tris(diphenyloxophosphoranyl)methanidodicyclohexylaminozirconium dimethyl, tris(diphenyloxophosphoranyl)methanidodiphenylphosphinozirconium dichloride, tris(diphenyloxophosphoranyl)methanidodiphenylphosphinozirconium dimethyl, tris(diphenyloxophosphoranyl)methanidodicyclohexylphosphinozirconium dichloride, tris(diphenyloxophosphoranyl)methanidodicyclohexylphosphinozirconium dimethyl, tris(diphenyloxophosphoranyl)methanidocyclopentadienylzirconium dichloride, tris(diphenyloxophosphoranyl)methanidocyclopentadienylzirconium dimethyl, tris(diphenyloxophosphoranyl)methanidobutylcyclopentadienylzirconium dichloride, tris(diphenyloxophosphoranyl)methanidobutylcyclopentadienylzirconium dimethyl, tris(diphenyloxophosphoranyl)methanidoindenylzirconium dichloride, tris(diphenyloxophosphoranyl)methanidoindenylzirconium dimethyl, tris(diphenyloxophosphoranyl)methanidotetra(n-butyl)indenylzirconium dichloride, tris(diphenyloxophosphoranyl)methanidotetra(n-butyl)indenylzirconium dimethyl, tris(diphenyloxophosphoranyl)methanidofluorenylzirconium dichloride, tris(diphenyloxophosphoranyl)methanidofluorenylzirconium dimethyl, tris(diphenylthiophosphoranyl)methanidozirconium trichloride, tris(diphenylthiophosphoranyl)methanidozirconium tribenzyl, tris(diphenylthiophosphoranyl)methanidozirconium trimethyl, tris(diphenylthiophosphoranyl)methanidodiisopropylaminozirconium dichloride, tris(diphenylthiophosphoranyl)methanidodiisopropylaminozirconium dimethyl, tris(diphenylthiophosphoranyl)methanidodi(t-butyl)aminozirconium dichloride, tris(diphenylthiophosphoranyl)methanidodicyclohexylaminozirconium dichloride, tris(diphenylthiophosphoranyl)methanidodiphenylphosphinozirconium dichloride, tris(diphenylthiophosphoranyl)methanidodicyclohexylphosphinozirconium dichloride, tris(diphenylthiophosphoranyl)methanidocyclopentadienylzirconium dichloride, tris(diphenylthiophosphoranyl)methanidobutylcyclopentadienylzirconium dichloride, tris(diphenylthiophosphoranyl)methanidoindenylzirconium dichloride, tris(diphenylthiophosphoranyl)methanidotetrahydroindenylzirconium dichloride, tris(diphenylthiophosphoranyl)methanidofluorenylzirconium dichloride, bis(diphenylphosphino)(diphenyloxophosphoranyl)methanidozirconium trichloride, bis(diphenylphosphino)(diphenyloxophosphoranyl)methanidozirconium tribenzyl, bis(diphenylphosphino)(diphenyloxophosphoranyl)methanidozirconium trimethyl, bis(diphenylphosphino)(diphenyloxophosphoranyl)methanidodiisopropylaminozirconium dichloride, bis(diphenylphosphino)(diphenyloxophosphoranyl)methanidodiisopropylaminozirconium dimethyl, bis(diphenylphosphino)(diphenyloxophosphoranyl)methanidodi(t-butyl)aminozirconium dichloride, bis(diphenylphosphino)(diphenyloxophosphoranyl)methanidodicyclohexylaminozirconium dichloride, bis(diphenylphosphino)(diphenyloxophosphoranyl)methanidodiphenylphosphinozirconium dichloride, bis(diphenylphosphino)(diphenyloxophosphoranyl)methanidodicyclohexylphosphinozirconium dichloride, bis(diphenylphosphino)(diphenyloxophosphoranyl)methanidocyclopentadienylzirconium dichloride, bis(diphenylphosphino)(diphenyloxophosphoranyl)methanidobutylcyclopentadienylzirconium dichloride, bis(diphenylphosphino)(diphenyloxophosphoranyl)methanidoindenylzirconium dichloride, bis(diphenylphosphino)(diphenyloxophosphoranyl)methanidotetrahydroindenylzirconium dichloride, bis(diphenylphosphino)(diphenyloxophosphoranyl)methanidofluorenylzirconium dichloride, tris(diphenylselenophosphoranyl)methanidozirconiumtrichloride, tris(diphenylselenophosphoranyl)methanidozirconium tribenzyl, tris(diphenylselenophosphoranyl)methanidozirconium trimethyl, tris(diphenylselenophosphoranyl)methanidodiisopropylaminozirconium dichloride, tris(diphenylselenophosphoranyl)methanidodiisopropylaminozirconium dimethyl, tris(diphenylselenophosphoranyl)methanidodi(t-butyl)aminozirconium dichloride, tris(diphenylselenophosphoranyl)methanidodicyclohexylaminozirconium dichloride, tris(diphenylselenophosphoranyl)methanidodiphenylphosphinozirconium dichloride, tris(diphenylselenophosphoranyl)methanidodicyclohexylphosphinozirconirnm dichloride, tris(diphenylselenophosphoranyl)methanidocyclopentadlenylzirconium dichloride, tris(diphenylselenophosphoranyl)methanidobutylcyclopentadienylzirconium dichloride, tris(diphenylselenophosphoranyl)methanidoindenylzirconium dichloride, tris(diphenylselenophosphoranyl)methanidotetrahydroindenylzirconium dichloride, tris(diphenylselenophosphoranyl)methanidofluorenylzirconium dichloride, bis(diphenylphosphino)(diphenylthiophosphoranyl)methanidozirconium trichloride, bis(diphenylphosphino)(diphenylthiophosphoranyl)methanidozirconium tribenzyl, bis(diphenylphosphino)(diphenylthiophosphoranyl)methanidozirconium trimethyl, bis(diphenylphosphino)(diphenylthiophosphoranyl)methanidodiisopropylaminozirconium dichloride, bis(diphenylphosphino)(diphenylthiophosphoranyl)methanidodiisopropylaminozirconium dimethyl, bis(diphenylphosphino)(diphenylthiophosphoranyl)methanidodi(t-butyl)aminozirconium dichloride, bis(diphenylphosphino)(diphenylthiophosphoranyl)methanidodihexylaminozirconium dichloride, bis(diphenylphosphino)(diphenylthiophosphoranyl)methanidodiphenylphosphinozirconium dichloride, bis(diphenylphosphino)(diphenylthiophosphoranyl)methanidodicyclohexylphosphinozirconium dichloride, bis(diphenylphosphino)(diphenylthiophosphoranyl)methanidocyclopentadienylzirconium dichloride, bis(diphenylphosphino)(diphenylthiophosphoranyl)methanidobutylcyclopentadienylzirconium dichloride, bis(diphenylphosphino)(diphenylthiophosphoranyl)methanidoindenylzirconium dichloride, bis(diphenylphosphino)(diphenylthiophosphoranyl)methanidotetrahydroindenylzirconium dichloride, bis(diphenylphosphino)(diphenylthiophosphoranyl)methanidofluorenylzirconium dichloride, (diphenyloxophosphoranyl)(diphenylthiophosphoranyl)(diphenylselenophosphoranyl)methanidozirconium trichloride, (diphenyloxophosphoranyl)(diphenylthiophosphoranyl)(diphenylselenophosphoranyl)methanidozirconium tribenzyl, (diphenyloxophosphoranyl)(diphenylthiphoranyl)(diphenylselenophosphoranyl)methanidozirconium trimethyl, (diphenyloxophosphoranyl)(diphenylthiophosphoranyl)(diphenylselenophosphoranyl)methanidodiisopropylaminozirconium dichloride, (diphenyloxophosphoranyl)(diphenylthiophosphoranyl)(diphenylselenophosphoranyl)methanidodiisopropylaminozirconium dimethyl, (diphenyloxophosphoranyl)(diphenylthiophosphoranyl)(diphenylselenophosphoranyl)methanidodi(t-butyl)aminozirconium dichloride, (diphenyloxophosphoranyl)(diphenylthiophosphoranyl)(diphenylselenophosphoranyl)methanidodicyclohexylaminozirconium dichloride, (diphenyloxophosphoranyl)(diphenylthiophosphoranyl)(diphenylselenophosphoranyl)methanidodiphenylphosphinozirconium dichloride, (diphenyloxophosphoranyl)(diphenylthiophosphoranyl)(diphenylselenophosphoranyl)methanidodicyclohexyl phosphinozirconium dichloride, (diphenyloxophosphoranyl)(diphenylthiophosphoranyl)diphenylselenophosphoranyl)methanidocyclopentadienylzirconium dichloride, (diphenyloxophosphoranyl)(diphenylthiophosphoranyl)(diphenylselenophosphoranyl)methanidobutylcyclopentadienylzirconium dichloride, (diphenyloxophosphoranyl)(diphenylthiophosphoranyl)(diphenylselenophosphoranyl)methanidoindenylzirconium dichloride, (diphenyloxophosphoranyl)(diphenylthiophosphoranyl)(diphenylselenophosphoranyl)methanidotetrahydroindenylzirconium dichloride, (diphenyloxophosphoranyl)(diphenylthiophosphoranyl)(diphenylselenophosphoranyl)methanidofluorenylzirconium dichloride, substituted compounds of the above compounds, and compounds having the same nomenclatures as those of the above compounds except that the term "methanido" is replaced with "hydroborato" or "C 1 - C 10 alkyl group-substituted borato". Class 2 (compounds having a combination of ligand L 1 and ligand L 2 wherein ligand L 1 is a group containing at least one phosphorus-containing group and ligand L 2 is a 5-membered heterocyclic ligand, represented by formula V, containing at least one trivalent atom selected from the group consisting of nitrogen, phosphorus, arsenic, antimony and bismuth atoms: tris(diphenyloxophosphoranyl)methanidopyrasolylzirconium dichloride, tris(diphenyloxophosphoranyl)methanido(3,4,5-trimethylpyrazolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanidoimidazolylzirconium dichloride, tris(diphenyloxophosphoranyl)methanido(1,2,3-triazolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanidotetraazolylzirconium dichloride, tris(diphenyloxophosphoranyl)methanido(1,2-diphospholyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanido(3,4,5-trimethyl-1,2-diphospholyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanido(1,3-diphospholyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanido(1,2,3-triphospholyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanidopentaphospholylzirconium dichloride, tris(diphenyloxophosphoranyl)methanido(1,2-diarsolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanido(3,4,5-trimethyl-1,2-diarsolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanido(1,3-diarsolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanido(1,2,3-triarsolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanidotetraarsolylzirconium dichloride, tris(diphenyloxophosphoranyl)methanido (1,2-distibolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanido(3,4,5-trimethyl-1,2-distibolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanido(1,3-distibolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanido(1,2,3-tristibolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanidotetrastibolylzirconium dichloride, tris(diphenyloxophosphoranyl)methanido(1,2-dibismolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanido(3,4,5-trimethyl-1,2-dibismolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanido(1,3-dibismolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanido(1,2,3-tribismolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanidotetrabismolylzirconium dichloride, tris(diphenyloxophosphoranyl)methanidopyrrolylzirconium dichloride, tris(diphenyloxophosphoranyl)methanido(2-methylpyrrolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanido(3,4-dimethylpyrrolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanido(2,3,4,5-tetrametylpyrrolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanidoindolylzirconium dichloride, tris(diphenyloxophosphoranyl)methanidocarbazolylzirconium dichloride, tris(diphenyloxophosphoranyl)methanidophospholylzirconium dichloride, tris(diphenyloxophosphoranyl)methanido(2-methylphospholyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanido(3,4-dimethylphospholyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanido(2,3,4,5-tetramethylphospholyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanidobenzo[b]phospholylzirconium dichloride, tris(diphenyloxophosphoranyl)methanidodibenzo[b,d]phospholylzirconium dichloride, tris(diphenyloxophosphoranyl)methanidoarsolylzirconium dichloride, tris(diphenyloxophosphoranyl)methanido(2-methylarsolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanido(3,4-dimethylarsolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanido(2,3,4,5-tetramethylarsolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanidobenzo[b]arsolylzirconium dichloride, tris(diphenyloxophosphoranyl)methanidodibenzo[b,d]arsolylzirconium dichloride, tris(diphenyloxophosphoranyl)methanidostibolylzirconium dichloride, tris(diphenyloxophosphoranyl)methanido(2-methylstibolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanido(3,4-dimethylstibolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanido(2,3,4,5-tetramethylstibolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanidobenzo[b]stibolylzirconium dichloride, tris(diphenyloxophosphoranyl)methanidodibenzo[b,d]stibolylzirconium dichloride, tris(diphenyloxophosphoranyl)methanidobismolylzirconium dichloride, tris(diphenyloxophosphoranyl)methanido(2-methylbismolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanido(3,4-dimethylbismolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanido(2,3,4,5-tetramethylbismolyl)zirconium dichloride, tris(diphenyloxophosphoranyl)methanidobenzo[b]bismolylzirconium dichloride, and tris(diphenyloxophosphoranyl)methanidodibenzo[b,d]bismolylzirconium dichloride. In place of the zirconium atom as a central metal of the above-mentioned zirconium compounds, other metals, such as titanium and hafnium, can be used. Further, in place of the anionic ligands used in the above-mentioned compounds, other types of non-coordinating anions can be used, so that a structure of the resultant compound is represented by formula XIII.Examples of compounds of formula XIV wherein M represents zirconium include those which can be classified into Class 3. Class 3 (compounds having a combination of ligand L 1 and ligand L 2 , wherein ligand L 1 is a group containing at least one phosphorous-containing groups, represented by formula III and ligand L 2 is selected from the group consisting of a ligand having a σ-bond and a ligand having a σ-bond and a bond selected from the group consisting of at least one π-bond and at least one lone electron pair donative bond, and wherein a bridge bond is formed between ligand L 1 and ligand L 2 ): bis(diphenyloxophosphoranyl)(2-(ethylene)phenylphenyloxophosphoranyl)methanidozirconium dichloride, bis(diphenyloxophosphoranyl)(2-(t-butylamino)phenylphenyloxophosphoranyl)methanidozirconium dichloride, bis(diphenyloxophosphoranyl)(2-(dimethylsilylene-t-butylamino)phenylphenyloxophosphoranyl)methanidozirconium dichloride, bis(diphenyloxophosphoranyl)(2-(cyclopentadienylene)phenylphenyloxophosphoranyl)methanidozirconium dichloride, bis(diphenyloxophosphoranyl)(2-(1-indenylene)phenylphenyloxophosphoranyl)methanidozirconium dichloride, and compounds having the same nomenclatures as those of the above compounds except that the term "methanido" is replaced with "hydroborato" or "C 1 - C 10 alkyl group-substituted borato". In place of the zirconium atom as a central metal of the above-mentioned zirconium compounds, other metals, such as titanium and hafnium, can be used. Further, in place of the anionic ligands used in the above-mentioned compounds, other types of non-coordinating anions can be used, so that a structure of the resultant compound is represented by formula XV. The catalyst of the present invention may be used alone for olefin polymerisation. However, the catalyst of the present invention may be used together with an auxiliary catalyst comprised of alkylaluminoxane which is represented by one of the following formulae XVI and XVII: wherein each R independently represents a hydrogen atom, a halogen atom or a C 1 - C 10 alkyl group, and n is an integer of from 1 to 40. Representative examples of Rs in formulae (XVI) and (XVII) include a hydrogen atom, a chlorine atom, a bromine atom, a methyl group, an ethyl group, an n-propyl group, an isoprolyl group, an n-butyl group, an isobutyl group, an s-butyl group, a propyl group, a hexyl group, a cyclohexyl group, a heptyl group, an octyl group, a nonyl group and a decyl group. It is preferred that at least one R represent a methyl group. The number of recurring units (i.e., n) is preferably in the range from 2 to 40, more preferably 5 to 40. The alkylaluminoxane can be prepared by a customary method. For example, in one customary method, trialkylaluminum is dissolved in a hydrocarbon solvent to obtain a solution and then, an equivalent amount of water, relative to the amount of the trialkylaluminum, is gradually added to the solution to hydrolyze the trialkylaluminum. In another customary method, copper sulfate hydrate or aluminum sulfate hydrate is suspended in a hydrocarbon solvent and then, trialkylaluminum (in an amount 1 to 3 equivalents relative to one equivalent of the crystal water of the suspended hydrate) is contacted with the hydrate to thereby gradually hydrolyze the trialkylaluminum. In still another customary method, silica gel having water adsorbed thereon is suspended in a hydrocarbon solvent and then, trialkylaluminum (in an amount 1 to 3 equivalents relative to one equivalent of the water adsorbed on the suspended silica gel) is contacted with the silica gel to thereby gradually hydrolyze the trialkylaluminum. Another example of an auxiliary catalyst which may be used together with the catalyst of the present invention is a cation producer represented by the following formula XVIII: [ On ] + [ An ] - wherein: [On] + represents a metal cation, such as a cation of a metal of Group IB, Group IIB or Group VIII of the Periodic Table of the Elements, or an onium, such as carbonium, silonium, oxonium, sulfonium, ammonium or phosphonium; and [An] - represents an anion which is stable under the reaction conditions for olefin polymerization and has no or poor coordinating properties. Preferred examples of cation producers represented by formula (XVIII) include tetra (pentafluorophenyl) borates, such as ferroceniumtetra(pentafluorophenyl) borate, silver (I) tetra(pentafluorophenyl)borate, copper (I) tetra(pentafluorophenyl)borate, mercury (II) bis(tetra(pentafluorophenyl)borate), palladium (II) bis(tetra(pentafluorophenyl)borate), platinum (II) bis(tetra(pentafluorophenyl)borate), diphenylhydrocarboniumtetra(pentafluorophenyl)borate, trihpenylcarboniumtetra(pentafluorophenyl)borate, triphenylsiloniumtetra(pentafluorophenyl)borate, tricyclohexylcarboniumtetra(pentafluorophenyl)borate, triethyloxoniumtetra(pentafluorophenyl)borate, triethylsulfoniumtetra(pentafluorophenyl)borate, diethylaniliniumtetra(pentafluorophenyl)borate, trimethylammoniumtetra(pentafluorophenyl)borate, triethylammoniumtetra(pentafluorophenyl)borate, tetra(n-butyl) ammoniumtetra(pentafluorophenyl)borate and triphenylphosphoniumtetra(pentafluorophenyl)borate. A further example of an auxiliary catalyst is an alkylaluminum represented by the following formula XIX: ( R 3 Al ) n wherein each R independently represents a hydrogen atom, a halogen atom and a C 1 - C 10 alkyl group, and n is 1 or 2. This auxiliary catalyst is effective for stabilizing the catalyst of the present invention and for stabilizing an alkylaluminoxane used as an auxiliary catalyst so that the amount of alkylaluminoxane to be used can be reduced. Examples of Rs include a hydrogen atom, a chlorine atom, a bromine atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a propyl group, a hexyl group, a cyclohexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group. It is preferred that at least one R represent a methyl group. In conducting olefin polymerization using the catalyst of the present invention, it is preferred that the catalyst of the present invention be used in an amount such that the concentration of the transition metal of the catalyst is in the range from 10 -10 to 10 -1 mol/liter of the liquid medium, more preferably from 10 -8 to 10 -3 mol/liter of the liquid medium. (When an olefin is polymerized in the gaseous phase, the "liquid medium" means a solvent to be used while when an olefin is polymerized is in the liquid phase, the "liquid medium" means the liquid olefin or a mixture of a solvent to be used and the liquid olefin). When olefin polymerization is conducted by a gas phase polymerization method, the catalyst is used in a form carried on a carrier. In this case, it is preferred that the amount of the transition metal of the catalyst be 10 -7 to 10 -2 gram atom/g of the carrier, more preferably 10 -5 to 10 -3 gram atom/g of the carrier. When alkylaluminoxane is used as an auxiliary catalyst, it is preferred that alkylaluminoxane be used in an amount such that the atomic ratio of the aluminum contained in the alkylaluminoxane to the transition metal contained in the catalyst is in the range from 1 to 10 6 , more preferably from 1 to 10 4 . When the above-mentioned cation producer is employed as an auxiliary catalyst, it is prefered that the cation producer be used in an amount such that the atomic ratio of the cation in the cation producer to the transition metal contained in the catalyst is in the range from 0.1 to 10, preferably from 0.5 to 2. In order to increase a bulk density of a polymer to be produced, improve the powder characteristics of the polymer, and control a molecular weight distribution of the polymer, the catalyst of the present invention can be used in a state carried on a carrier. Examples of materials for carriers include an organic material, such as starch or a polymer, a metallic material, such as bismuth, powdery copper or powdery iron, a metal oxide, such as alumina or iron oxide, a metal carbonate, such as magnesium carbonate, a metal chloride, such as magnesium chloride, activated carbon, an inorganic carbide, such as silicon carbide, an inorganic silicon oxide, such as silica, zeolite or diatomite and an ion-exchange resin, such as Amberlite or Nafion. Generally, these carrier materials contain an active hydrogen-containing compound, such as crystal water, adsorbed water or a hydroxyl group, which can react with the catalyst to deactivate the same. Therefore, it is preferred that before introduction into the reaction system, these carrier materials be subjected to appropriate treatment for removing the active hydrogen. For example, in such a treatment, active hydrogen atoms, which are contained in the hydroxy groups of an organic material, in the silanol groups of an inorganic silicon oxide or in the amino groups or hydroxyl groups of an ion-exchange resin, can be removed by contacting carriers containing the active hydrogen atoms with alkylaluminum or alkylaluminoxane (which is used in an amount 0.3 to 5 equivalents (in terms of aluminum atoms) relative to one equivalent of the active hydrogen atom. With respect to carrier materials composed of a metal, a metal oxide, a metal carbonate, a metal chloride, an inorganic carbonate, inorganic silicon oxide and the like, the crystal water and adsorbed water of these carriers can be removed therefrom by sintering these carrier materials at an appropriate temperature. The treatment for removing the active hydrogen from a carrier can be conducted before or after a catalyst is carried on the carrier. At least one of the catalyst of the present invention, the alkylaluminoxane auxiliary catalyst, the cation producer as an auxiliary catalyst and the alkylaluminum auxiliary catalyst can be carried on a carrier in any combination and in any order. Hereinafter, explanation is made on the polymerization of an olefin using the catalyst of the present invention. The catalyst of the present invention can be advantageously used for polymerization of various olefins. Examples of olefins which can be polymerized using the catalyst of the present invention include an α-olefin, such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene or vinylcyclohexane; a vinyl aromatic hydrocarbon, such as styrene or methylstyrene; an alicyclic olefin, such as cyclopentene, methylcyclopentene, cycloheptene, or cyclooctene; a conjugated diene, such as butadiene, 1,3-pentadiene, 1,3-hexadiene, cyclopentadiene, 1,3-cyclohexadiene or vinyl-1-cyclohexene; an unconjugated diene, such as 1,4-pentadiene, 1,5-hexadiene, 1,4-hexadiene, 2-methyl-1,4-pentadiene, 3-vinylcyclohexene or 4-vinyl-3-norbornene; a polyene having 6 to 20 carbon atoms; acetylene; propyne; butyne; pentyne; and hexyne. Of them, an α-olefin is preferred and ethylene is more preferred. The catalyst of the present invention can also be used for copolymerization between two or more different types of olefins. For example, there can be mentioned copolymerization between ethylene and one or more comonomers, e.g., an α-olefin, such as propylene, 1-butene or 1-hexene; a vinylaromatic hydrocarbon, such as styrene or methylstyrene; an alicyclic olefin, such as cyclopentene or methylcyclopentene; a conjugated diene, such as butadiene; an unconjugated diene, such as 1,5-hexadiene or 3-vinylcyclohexene; a polyene; and acetylene. In connection with the above, it is noted that the types of catalysts are not particularly limited with respect to the types of olefins to be polymerized, For the polymerization of an olefin, there may be employed a customary polymerization method, such as a suspension polymerization method, a solution polymerization method and a gas phase polymerization method. In a suspension polymerization method, for example, a catalyst is charged, together with a polymerization solvent, in a reaction vessel and then, thereto is added an olefin in an inert atmosphere under a pressure of 1 to 200 kg/cm 2 G. A polymerization reaction is then allowed to proceed at a temperature of from -50 °C to 120 °C. Examples of solvents to be used in the polymerization reaction include aliphatic hydrocarbons, such as propane, butane, pentane, hexane, heptane, octane and nonane; alicyclic hydrocarbons, such as cyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane, cyclooctane and isopropylcyclohexane; aromatic hydrocarbons, such as benzene, toluene, xylene and t-butylbenzene; perfluoro aliphatic hydrocarbons, such as perfluorooctane and perfluorononane, and mixtures of these hydrocarbons. In a solution polymerization method, for example, a catalyst is introduced, together with a polymerization solvent, in a reaction vessel and then, thereto is added an olefin in an inert atmosphere under a pressure of from 1 to 200 kg/cm 2 G. A polymerization reaction is allowed to proceed at a temperature of from 50 °C to 300 °C. Examples of solvents to be used in the polymerization reaction include aliphatic hydrocarbons, such as propane, butane, pentane, hexane, heptane, octane and nonane; alicyclic hydrocarbons, such as cyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane, cyclooctane and isopropylcyclohexane; aromatic hydrocarbons, such as benzene, toluene, xylene and t-butylbenzene; perfluoro aliphatic hydrocarbons, such as perfluorooctane and perfluorononane, and mixtures of these hydrocarbons. In a gas phase polymerization method, for example, a catalyst is placed in a reaction vessel and an olefin is charged in the reaction vessel in an inert atmosphere under a pressure of from 1 to 50 kg/cm 2 G. A polymerization reaction is allowed to proceed at a temperature of from -50 °C to 120 °C. During the polymerization, frequency of contact between olefin molecules and the catalyst molecules can be increased by employng a mixing apparatus, such as a fluidized bed or a moving bed, or by stirring . The polymerization may be conducted by a mono-stage polymerization method in which a single reaction stage is employed, or by a multi-stage polymerization method in which a plurality of reaction stages are involved. In the case of the multi-stage polymerization method, when the polymerization reaction is conducted using two or more different sets of reaction conditions, a polymer having a broad molecular weight distribution can be produced. If desired for controlling a molecular weight of a polymer to be produced, customary techniques may be employed, such as controlling of the reaction temperature and an addition of hydrogen to the reaction system. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The present invention will now be described in greater detail with reference to the following Examples and Comparative Examples which should not be construed as limiting the scope of the present invention. In the Examples and Comparative Examples, a catalytic activity represents an yield (g) of a polymer formed per gram of a metal contained in a catalyst per hour. Further, MI represents a melt index which is measured at a temperature of 190 °C under a load of 2.16 kg, while HMI represents a melt index measured at 190 °C under a load of 21.6 kg. Both of MI and HMI are measured according to ASTM D-1238. A molecular weight and a molecular weight distribution of a polymer are obtained, from a differential refractive index and viscosity, by gel permeation chromatography (apparatus: 150 CV manufactured and sold by Waters Assoc. Co., U.S.A.). Mw represents a weight average molecular weight, and Mn represents a number average molecular weight. [Polymerization of ethylene] Example 1 Synthesis of compound for ligand L 1 Trisdiphenyloxophosphoranylmethane (HTriso) for L 1 is synthesized according to the method described in "Inorganic Chemistry", page 2699 (1986). Synthesis of catalyst A1 Trisdiphenyloxophosphoranylmethanidocyclopentadienylzirconium dichloride {TrisoCpZrCl 2 }, wherein Triso represents a trisdiphenyloxophosphoranylmethanido group, and Cp represents a cyclopentadienyl group, is synthesized as follows. A 1-liter four-necked flask provided with a reflux column which is connected at a top thereof to a gas buret for measuring an amount of a generated gas, a dropping funnel, a stirrer and a thermometer is purged with nitrogen gas. To the flask is charged 360 mg of a 60 % oil dispersion of sodium hydride which has been washed with hexane. Thereto is added 500 ml of dried and distilled tetrahydrofuran and then, stirring is conducted to obtain a suspension. When 4.9 g of HTriso is added to the suspension, 200 ml of hydrogen gas is generated. When the generation of hydrogen gas ceases, 1.9 g of zirconium chloride is added thereto to obtain a mixture. The obtained mixture is stirred at room temperature for 4 hours. Subsequently, 100 ml of a tetrahydrofuran solution of cyclopentadienyl lithium (0.08 mmole/liter) is dropwise added thereto and then, a reaction is allowed to proceed for 4 hours. The reaction mixture is filtered through diatomaceous earth in nitrogen atmosphere to obtain a filtrate. After the filtrate is concentrated 5-fold, hexane is added to the concentrate, so that a white solid is precipitated. The precipitate is separated by filtration and then, recrystallized to obtain a product. Identification of the product as TrisoCpZrCl 2 is made by 1 H-NMR spectroscopy (heavy toluene, 270 MH), which shows signals for the ligand at δ 6.55 (S, 5H, Cp group), 6.8-7.2 (m, 27H, phenyl group) and 7.7-8.2 (m, 18H, phenyl group). Infrared (IR) spectrum shows a peak for the ligand at 1,115 (P=O) and 840 (Cp) cm -1 . Polymerization reaction A 3 ml toluene solution containing 0.1 µmole of catalyst A1 (TrisoCpZrCl 2 ) and 0.14 ml (0.4 mmole in terms of the amount of aluminum) of a toluene solution of methylaluminoxane (PMAO; containing 2.92 moles of aluminum/liter of the toluene solution) (manufactured and sold by Tosoh Akzo Corp., Japan) are charged, together with 0.8 liter of dehydrated and deoxygenated toluene, in a 1.6-liter autoclave evacuated and replaced with nitrogen gas. The temperature of the inside of the autoclave is maintained at 80 °C and then, ethylene gas is charged in the autoclave at a pressure of 10 kg/cm 2 G. A total pressure of the autoclave becomes 10.4 kg/cm 2 G, including a solvent pressure. A polymerization reaction is allowed to proceed for 1 hour, while the total pressure of the autoclave is maintained constantly by supplying ethylene gas. 9.7 g of a polymer is obtained. It is found that a catalytic activity of A1 is 1,070 kg/g of Zr per hour, the molecular weight of the polymer is 111,400 and the molecular weight distribution is 2.52 in terms of Mw/Mn. As is apparent from the above, the polymer produced using the catalyst A1 has a high molecular weight. Example 2 Synthesis of catalyst A2 Trisdiphenyloxophosphoranylmethanidoindenylzirconium dichloride {TrisoIndZrCl 2 } is synthesized as follows. Substantially the same procedure as described in Example 1 for preparing catalyst A1 is repeated except that a tetrahydrofuran solution of indenyllithium is used instead of the tetrahydrofuran solution of cyclopentadienyllithium. Identification of catalyst A2 is made by 1 H-NMR spectroscopy (heavy toluene, 270 MH), which shows signals for the ligand at δ 6.8-7.7 (m, 34H, indenyl group and phenyl group) and 7.8-8.2 (m, 18H, phenyl group). Polymerization reaction Substantially the same polymerization procedure as described in Example 1 is repeated except that a 3 ml toluene solution containing 0.1 µmole of catalyst A2 is used instead of catalyst A1. 4.4 g of a polymer is obtained. It is found that a catalytic activity of catalyst A2 is 484 kg/g of Zr per hour. Example 3 Synthesis of catalyst A3 Trisdiphenyloxophosphoranylmethanidozirconium trichloride {TrisoZrCl 3 } is synthesized as follows. In the same apparatus as used in Example 1 for synthesizing catalyst A1 is charged 360 mg of a 60 % oil dispersion of sodium hydride which has been washed with hexane. Thereto is added 500 ml of dried and distilled tetrahydrofuran to obtain a suspension. When 4.9 g of HTriso is added to the suspension, 200 ml of hydrogen gas is generated. When the generation of hydrogen gas ceases, 1.9 g of zirconium chloride is added thereto and then, a reaction is allowed to proceed while stirring at room temperature for 4 hours. The reaction mixture is filtered through diatomaceous earth in nitrogen atmosphere to obtain a filtrate. After the filtrate is concentrated 5-fold, hexane is added to the concentrate, so that a white solid is precipitated. The precipitate is separated by filtration and then, recrystallized to obtain a product. Identification of the product as {TrisoZrCl 3 } is made by 1 H-NMR spectroscopy (heavy toluene, 270 MH), which shows signals for ligand at δ 6.8 (m, 27 H, phenyl group) and 7.7-8.2 (m, 18 H, phenyl group), although high sensitivity is not obtained due to the poor solubility of the product in heavy toluene. IR spectrum shows a peak for the ligand at 1,114 (P=O) cm -1 . Polymerization reaction Substantially the same polymerization procedure as described in Example 1 is repeated except that a 3 ml toluene solution containing 0.5 µmole of catalyst A3 (TrisoZrCl 3 ) is used instead of catalyst A1. 5.2 g of a polymer is obtained. It is found that a catalytic activity of catalyst A3 is 114 kg/g of Zr per hour. Example 4 Synthesis of catalyst A4 Trisdiphenyloxophosphoranylmethanidozirconium trimethyl {TrisoZrMe 3 } is synthesized as follows. In the same apparatus as used in Example 1 for synthesizing catalyst A1 are charged 10 mmoles of catalyst A3 and 50 ml of diethyl ether cooled at -78 °C. Subsequently, 30 ml of 1 M diethyl ether solution of methyllithium is added dropwise thereto over a period of 1 hour through a dropping funnel. A formed solid is separated by filtration to obtain a filtrate. The obtained filtrate is concentrated to 10 ml. To the concentrate is added dried pentane to obtain a white precipitate. The precipitate is separated by filtration, followed by drying to obtain a product. Polymerization reaction Substantially the same polymerization procedure as described in Example 1 is repeated except that a 3 ml toluene solution containing 0.5 µmole of catalyst A4 (TrisoZrMe 3 ) is used instead of catalyst A1. 7.8 g of a polymer is obtained. It is found that a catalytic activity of catalyst A4 is 171 kg/g of Zr per hour. Example 5 Synthesis of catalyst A5 Trisdiphenyloxophosphoranylmethanidozirconium tribenzyl {TrisoZr(CH 2 Ph) 3 } is synthesized as follows. In the same apparatus as used in Example 1 for synthesizing catalyst A1 are charged 10 mmoles of catalyst A3 and 50 ml of diethyl ether cooled at -78 °C. Subsequently, 30 ml of 1 M diethyl ether solution of benzylmagnesium chloride, PhCH 2 MgCl is dropwise added thereto through a dropping funnel over a period of 1 hour. A formed solid is separated by filtration to obtain a filtrate. The obtained filtrate is concentrated to 10 ml. To the concentrate is added dried pentane to cause crystallization. Polymerization reaction Substantially the same polymerization procedure as described in Example 1 is repeated except that a 3 ml toluene solution containing 0.1 µmole of catalyst A5 {TrisoZr(CH 2 Ph) 3 } is used instead of catalyst A1. 2.1 g of a polymer is obtained. It is found that a catalytic activity of catalyst A5 is 230 kg/g of Zr per hour. Example 6 Synthesis of catalyst B2 2,3,4,5-tetramethylphospholyllithium {LiC 4 Me 4 P} is synthesized according to the method described in "Organometallics", page 921 (1988). Subsequently, (2,3,4,5-tetramethylphospholyl)(trisdiphenyloxophosphoranylmethanido)zirconium dichloride {(C 4 Me 4 P)(Triso)ZrCl 2 } is synthesized as follows. A 50 ml diethyl ether solution containing 10 mmoles of catalyst A3 is charged in a Schlenk's tube and cooled at -78 °C. Subsequently, 10 ml of 10 M diethyl ether solution of 2,3,4,5-tetramethylphospholyllithium {LiC 4 Me 4 P} is dropwise added thereto through a dropping funnel over a period of 1 hour to obtain a reaction mixture. The reaction mixture is further stirred for 8 hours. The resultant mixture is filtered through diatomaceous earth in nitrogen atmosphere to obtain a filtrate. After the filtrate is concentrated 5-fold, hexane is added to the concentrate, so that a slightly yellowish solid is precipitated. The precipitate is separated by filtration and then, recrystallized to obtain a product. Identification of the product as {(C 4 Me 4 P)(Triso)ZrCl 2 } is made by 1 H-NMR spectoscopy (heavy toluene, 270 MH), which shows signals for the ligand at δ 1.9 (s, 6 H, a methyl group, 2.1 (m, 6 H, a methyl group), 6.8 (m, 27 H, a phenyl group) and 7.7-8.2 (m, 18 H, a phenyl group), although high sensitivity is not obtained due to the poor solubility of the product in heavy toluene. Polymerization reaction Substantially the same polymerization procedure as described in Example 1 is repeated except that a 1 ml toluene suspension containing 1.0 µmole of catalyst B2 {(C 4 Me 4 P)(Triso)ZrCl 2 } and 0.5 ml of a toluene solution of methylaluminoxane (PMAO; containing 1.0 mmole of aluminum/0.5 ml of the toluene solution) (manufactured and sold by Ethyl Corporation, U. S. A.) are used instead of catalyst A1. 31 g of a polymer is obtained. It is found that a catalytic activity of catalyst B2 is 340 kg/g of Zr per hour. Comparative Example 1 Synthesis of comparative catalyst a Pyrazolylcyclopentadienylzirconium dichloride {pzCpZrCl 2 } is synthesized as follows. To a 100 ml diethyl ether solution containing 0.011 mole of pyrazolyllithium salt is gradually added 0.01 mole of zirconium chloride, followed by stirring for one day. Subsequently, 100 ml of a diethyl ether solution of cyclopentadienelithium salt is added to the mixture and then, stirred for one day. Subsequently, the ether is evaporated under a vacuum and then, pentane is added thereto to precipitate lithium chloride. The precipitate is separated by filtration to obtain a filtrate. The obtained filtrate is filtered two times through sellaite to obtain a catalyst in a solid form. Polymerization reaction A 3 ml toluene solution containing 1.0 µmole of {pzCpZrCl 2 } and 0.7 ml (2.0) mmoles in terms of the amount of aluminum) of a toluene solution of methylaluminoxane (PMAO; containing 2.92 moles of aluminum/liter of the toluene solution) (manufactured and sold by Tosoh Akzo Corp., Japan) are charged, together with 0.8 liter of dehydrated and deoxygenated toluene, in a 1.6-liter autoclave evacuated and replaced with nitrogen gas. The temperature of the inside of the autoclave is maintained at 80 °C and then, ethylene gas is charged in the autoclave at a pressure of 10 kg/cm 2 G. A total pressure of the autoclave becomes 10.4 kg/cm 2 G, including a solvent pressure. A polymerization reaction is allowed to proceed for 1 hour, while the total pressure of the autoclave is maintained constantly by supplying ethylene gas. 0.6 g of a polymer is obtained. It is found that a catalytic activity of comparative catalyst a having a monodentate ligand containing a hetero atom is as low as 6.6 kg/g of Zr per hour. Comparative Example 2 Synthesis of comparative catalyst intermediate I1 Hydrotrispyrazolylboratozirconium trichloride {HB(pz) 3 ZrCl 3 } is synthesized according to the method described in "Inorganic Chemistry", page 1065 (1983). Polymerization reaction Substantially the same polymerization procedure as described in Comparative Example 1 is repeated except that a 3 ml toluene solution containing 1.0 µmole of comparative catalyst intermediate I1 {HB(pz) 3 ZrCl 3 } is used instead of {pzCpZrCl 2 }. 2.6 g of a polymer is obtained. It is found that a catalytic activity of comparative catalyst intermediate I1 having only a trispyrazolyl ligand is as low as 29 kg/g of Zr per hour. Comparative Example 3 Synthesis of comparative catalyst intermediate I2 Hydrotris(3,5-dimethylpyrazolyl)boratozirconium trichloride {HB(3,5-Me 2 pz) 3 ZrCl 3 } is synthesized according to the method described in "Inorganic Chemistry", page 840(1982). Polymerization reaction Substantially the same polymerization procedure as described in Comparative Example 1 is repeated except that a 3 ml toluene solution containing 1.0 µmole of comparative catalyst intermediate I2 {HB(3,5-Me 2 pz) 3 ZrCl 3 } is used instead of {pzCpZrCl2}. 1.8 g of polymer is obtained. It is found that a catalytic activity of comparative catalyst intermediate I2 having only a trispyrazolyl ligand is as low as 20.1 kg/g of Zr per hour. Polymerization of propylene Example 7 Polymerization reaction 0.4 liter of dehydrated and deoxygenated liquid propylene is charged in a 1.6-liter autoclave evacuated and replaced with nitrogen gas. Subsequently, 1.4 ml (4.0 mmoles in terms of the amount of aluminum) of a toluene solution of methylaluminoxane (PMAO; containing 2.92 moles of aluminum/liter of the toluene solution) (manufactured and sold by Tosoh Akzo Corp., Japan) is charged in the autoclave, together with 0.1 liter of the liquid propylene. Finally, a 3 ml toluene suspension containing catalyst A1 (TrisoCpZrCl 2 ) (1.0 µmole) is charged, together with 0.1 liter of the liquid propylene in the autoclave. A polymerization reaction is allowed to proceed for 1 hour, while the temperature of the inside of the autoclave is maintained at 50 °C. 13.3 g of a jellylike polymer is obtained. It is found that the polymer is an atactic polypropylene, and that the catalytic activity of catalyst A1 is 146 kg/g of Zr per hour. [Copolymerization of ethylene and 1-hexene] Examples 8 and 11 Copolymerization reaction In a 1.6-liter autoclave evacuated and replaced with nitrogen gas are charged dehydrated and deoxygenated toluene and 1-hexene so that the total volume of toluene and 1-hexene is 800 ml (The volume of 1-hexene charged is indicated-in Table 1). The autoclave is connected at a top thereof to a gas feed line and containers 1 to 3 which have been, respectively, charged with a toluene solution of a catalyst (1 µmole/3 ml) indicated in Table 1 in an amount indicated in Table 1, auxiliary catalyst MMAO also in an amount indicated in Table 1, and methanol. Each of containers 1 to 3 has a valve at a top and a bottom thereof individually, and each of containers 1 and 2 is connected to a toluene tank by means of a pipe through a pump. Then, ethylene gas is introduced into the autoclave through the gas feed line under a pressure of 10 kg/cm 2 G, while maintaining the internal temperature of the autoclave at 70 °C. A total pressure of the autoclave becomes about 11.5 kg/cm 2 G, including solvent pressure. 50 ml of toluene is fed from the tank to container 2 by means of the pump, and the top and bottom valves of container 2 are opened simultaneously, to thereby introduce auxiliary catalyst MMAO into the autoclave with toluene. Then, 50 ml of toluene is also fed from the tank to container 1 by means of the pump, and the top and bottom valves of container 1 are opened simultaneously, to thereby introduce the catalyst into the autoclave with toluene. Thereafter, a polymerization reaction is allowed to proceed for 1 hour, while the total pressure of the autoclave is maintained constantly by supplying ethylene gas and controlling the secondary pressure of a reducing valve connected to the autoclave. 10 ml of methanol is introduced in the autoclave, to thereby terminate the reaction. The amounts of a monomer and catalyst, reaction conditions, and yield and properties of the obtained copolymer are shown in Table 1. 5, 30 and 60 minutes after initiation of the copolymerization reaction, the rates of absorption of ethylene in Example 26 are 0.014 mole/min, 0.016 mole/min and 0.018 mole/min, respectively. Any lowering in absorption rate is not observed. Example No. 1-hexene amount (ml) Catalyst MMAO mmol Polymer obtained (g) Activity Molecular weight Density (g/cm 3 ) Type µmol kg/gZrhr Mw Mw/Mn 8 60 A1 0.1 0.2 9.7 1,070 821,000 2.53 0.926 9 120 A1 0.1 0.2 9.0 990 664,000 2.87 0.915 10 60 A2 1.0 2.0 16.2 178 1,156,000 3.09 0.945 11 120 A2 1.0 2.0 14.4 158 1,407,000 3.01 0.938 1) Total volume of toluene and 1-hexene is adjusted to 800 ml. 2) MMAO type 4 (manufactured and sold by Tosoh Akzo Corp. Japan) is used as an auxiliary catalyst, the amount of which is indicated in terms of the amount of aluminum (mmole). [Polymerization of styrene] Examples 12 and 13 Synthesis of catalyst D4 Trisdiphenyloxophosphoranylmethanidotitanium trichloride {TrisoTiCl 3 } is synthesized as follows. Substantially the same procedure as described in Example 3 for synthesizing catalyst A3 is repeated except that 1.6 g of titanium chloride is used instead of zirconium chloride. Identification of catalyst D4 is made by 1 H-NMR spectroscopy (heavy toluene, 270 MH), which shows signals of the ligands at δ6.8-7.7 (m, 27H, a phenyl group) and 7.7-8.2 (m, 18H, a phenyl group). IR spectrum shows a peak for the ligand at 1,115 (P=O) cm -1 . Synthesis of catalyst D5 Trisdiphenyloxophosphoranylmethanidotitanium trimethyl {TrisoTiMe 3 } is synthesized as follows. In the same apparatus as used in Example 1 for synthesizing catalyst A1 are charged 10 mmoles of catalyst D4 and 50 ml of diethyl ether cooled at -78 °C. Subsequently, thereto dropwise added is 30 ml of 1 M diethyl ether solution of methyllithium over a period of 1 hour. A formed solid is filtered off to obtain a filtrate. The obtained filtrate is condensed to 10 ml and then, thereto added is dried pentane to obtain a white precipitate. The precipitate is separated by filtration, followed by drying to obtain a product. Polymerization reaction of styrene In a 1.6-liter autoclave evacuated and replaced with nitrogen gas are charged 300 ml of dehydrated and deoxygenated toluene and 300 ml of stylene obtained by vacuum distillation. The autoclave is connected at a top thereof to containers 1 to 3 which have been, respectively, charged with a toluene solution of catalyst (1 µmole/3 ml) indicated in Table 2 in an amount indicated in Table 2, auxiliary catalyst MMAO also in an amount indicated in Table 2, and methanol. Each of containers 1 to 3 has a valve at a top and a bottom thereof, and each of containers 1 and 2 is connected to a toluene tank by means of a pipe through a pump. 50 ml of toluene is fed from the tank to container 2 by means of the pump, and the top and bottom valves of container 2 are opened simultaneously, to thereby introduce auxiliary catalyst MMAO into the autoclave with toluene. Then, 50 ml of toluene is also fed from the tank to container 1 by means of the pump, and the top and bottom valves of container 1 are opened simultaneously, to thereby introduce catalyst indicated in Table 2 into the autoclave with toluene. Thereafter, a polymerization reaction is allowed to proceed for 2 hours. 10 ml of methanol is introduced into the autoclave, to thereby terminate the reaction. Results of Examples 12 and 13 are shown in Table 2. Example No. Catalyst MMAO mmol Polymer obtained MEK extraction residue % Melting point °C Type µmol g kg/gZrhr 12 D4 10.0 4.0 99.4 103 5 97 270 13 D5 10.0 4.0 88.7 92.4 97 270 Note: (1) Melting point of the obtained polymer is measured by DSC. (2) The obtained polymer is cut to obtain pieces thereof. The obtained pieces are subjected to extraction with methylethyl ketone (MEK) by means of Soxhlet's extractor. The residue is weighed to obtain MEK extraction residue (%), based on the weight of the polymer pieces.

Claims: An olefin polymerization catalyst comprising at least one transition metal compound selected from compounds of formulae I and II: wherein: M is a transition metal selected from the group consisting of metals of Groups IIIA including the lanthanide series, IVA, VA, VIA, VIIA and VIII of the Periodic Table of the Elements, X is an anionic ligand, n is an integer represented by formula G-2 in which G is the Group number of the Group of the Periodic Table to which said transition metal belongs, and L 1 and L 2 are ligands defined below, wherein a bridge bond is optionally formed between L 1 and L 2 ; and wherein: M, X, n, L 1 and L 2 are as defined for formula (I), and J is a non-coordinating anion; said ligand L 1 being a group, containing at least one phosphorus-containing group, represented by formula III: wherein: A is a carbon atom, or a boron atom substituted with a substituent selected from the group consisting of: a hydrogen atom, a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group or at least one halogen atom, a C 6 - C 20 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group or at least one halogen atom, an oxy group which is substituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a thio group which is substituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a silyl group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group, at least one C 6 - C 20 aromatic hydrocarbon group or at least one halogen atom, a siloxy group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group, at least one C 6 - C 20 aromatic hydrocarbon group or at least one halogen atom, an amino group which is N,N-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group, and a phosphino group which is P,P-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group; {R 1 R 2 (Q=)P} represents a phosphorus-containing group, in which: P is a trivalent or pentavalent phosphorus atom, each of R 1 and R 2 is monovalent and independently represents a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group or at least one halogen atom, or a C 6 - C 20 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group or at least one halogen atom, and Q is divalent and represents a divalent atom of O, S or Se, or a lone electron pair; and each of Z 1 and Z 2 independently represents a phosphorus-containing group of formula {R 1 R 2 (Q=)P} as defined above, or a pyrazolyl group represented by formula IV: wherein: each of R 3 , R 4 and R 5 independently represents: a hydrogen atom, a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group or at least one halogen atom, a C 6 - C 20 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group or at least one halogen atom, an oxy group which is substituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a thio group which is substituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a silyl group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 -C 20 aliphatic hydrocarbon group, at least one C 6 - C 20 aromatic hydrocarbon group or at least one halogen atom, a siloxy group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 -C 20 aliphatic hydrocarbon group, at least one C 6 - C 20 aromatic hydrocarbon group or at least one halogen atom, an amino group which is N,N-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group, and a phosphino group which is P,P-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group, wherein a bridge bond is optionally formed between R 3 and R 4 or between R 3 and R 5 , and said ligand L 2 being selected from the group consisting of a ligand having a σ-bond and a ligand having a σ-bond and a bond selected from the group consisting of at least one π-bond and at least one lone electron pair donative bond. The catalyst according to claim 1, wherein said transition metal of each of formulae I and II is from Group IVA of the Periodic Table. The catalyst according to claim 2, wherein said transition metal is selected from the group consisting of Ti, Zr and Hf. The catalyst according to any one of claims 1 to 3, wherein each of Z 1 and Z 2 of formula III independently represents a phosphorus-containing group of formula {R 1 R 2 (Q=)P} as defined for formula III. The catalyst according to claim 4, wherein said ligand L 1 represented by formula III is tris(diphenyloxophosphoranyl)methanide. The catalyst according to any one of claims 1 to 5, wherein said Ligand L 2 is a ligand having a σ-bond and at least one π-bond and being a 5-membered heterocyclic ligand represented by formula V: {E m (CR 6 ) 5-m } - wherein: each R 6 independently represents: a hydrogen atom, a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group or at least one halogen atom, a C 6 - C 20 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group or at least one halogen atom, an oxy group which is substituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a thio group which is substituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a silyl group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group, at least one C 6 - C 20 aromatic hydrocarbon group or at least one halogen atom, a siloxy group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group, at least one C 6 - C 20 aromatic hydrocarbon group or at least one halogen atom, an amino group which is N,N-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group, and a phosphino group which is P,P-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group, m is an integer of from 1 to 5, each E independently represents a trivalent atom selected from nitrogen, phosphorus, arsenic, antimony and bismuth atoms, wherein a bridge bond is optionally formed between neighboring R 6 and R 6 . The catalyst according to any one of claims 1 to 5, wherein said ligand L 2 is a ligand having a σ-bond and at least one π-bond and being an alkadienyl ligand. The catalyst according to any one of claims 1 to 7, further comprising an auxiliary catalyst comprised of an alkylaluminoxane.

Inventors: AOKI TOSHIYA, KANESHIMA TOKITAKA, AOKI, TOSHIYA, KANESHIMA, TOKITAKA
Applicants: ASAHI CHEMICAL IND, ASAHI KASEI KOGYO KABUSHIKI KAISHA
Application year: 1994
Main classification: C08F4
IPC codes: C08F210, C08F4, C08F110, C08F10